At this time, DCE will only remove an instruction if it is a combinator.
However, there are certain non-combinator instructions that can be
safely removed if their results are not used. The derivative
instructions are on example.
We are also missing some instructions from the list of combinators
those are added as the same time.
When doing if-conversion, we do not currently move code out of the side
nodes. The reason for this is that it can increase the number of
instructions that get executed because both side nods will have to be
executed now.
In this commit, we add code to move an instruction, and all of the
instructions it depends on, out of a side node and into the header of
the selection construct. However to keep the cost down, we only do it
when the two values in the OpPhi node compute the same value. This way
we have to move only one of the instructions and the other becomes
unused most of the time. So no real extra cost.
Makes the value number table an alalysis in the ir context.
Added more opcodes to list of code motion safe opcodes.
Fixes#1526.
Previously, the loop class used the terms latch and continue block
interchangeably. This patch splits the two and corrects and tests some
uses of the old uses of GetLatchBlock.
This pass will look for adjacent loops that are compatible and legal to
be fused.
Loops are compatible if:
- they both have one induction variable
- they have the same upper and lower bounds
- same initial value
- same condition
- they have the same update step
- they are adjacent
- there are no break/continue in either of them
Fusion is legal if:
- fused loops do not have any dependencies with dependence distance
greater than 0 that did not exist in the original loops.
- there are no function calls in the loops (could have side-effects)
- there are no barriers in the loops
It will fuse all such loops as long as the number of registers used for
the fused loop stays under the threshold defined by
max_registers_per_loop.
Adds support for spliting loops whose register pressure exceeds a user
provided level. This pass will split a loop into two or more loops given
that the loop is a top level loop and that spliting the loop is legal.
Control flow is left intact for dead code elimination to remove.
This pass is enabled with the --loop-fission flag to spirv-opt.
Track live scalars in VDCE as if they were single element vectors.
Handle the extended instructions for GLSL in VDCE.
Handle composite construct instructions in VDCE.
If one of the operands to an OpVectorTimesScalar instruction is zero,
then the result will be the 0 vector. Currently we do not fold the
insturction unless both operands are constants. This change fixes that.
We also allow folding of OpPhi instructions where the incoming values
are either an OpUndef or the OpPhi instruction itself. As with other
cases, this can be simplified to the OpUndef.
Track live scalars in VDCE as if they were single element vectors.
Handle the extended instructions for GLSL in VDCE.
Handle composite construct instructions in VDCE.
Fixes#1511.
Eliminate unused store to variable if followed by store to same
variable in same block.
Most significantly, this cleans up stores made unused by this pass.
These useless stores can inhibit subsequent optimizations, specifically
LocalSingleStoreElim. Eliminating them makes subsequent optimization more
effective.
The main effect of this pass is to simplify the work done by the SSA
rewriter. It catches many local loads/stores that help speeding up the
work done by the main rewriter.
Introduce a pass that does a DCE type analysis for vector elements
instead of the whole vector as a single element.
It will then rewrite instructions that are not used with something else.
For example, an instruction whose value are not used, even though it is
referenced, is replaced with an OpUndef.
For each function, the analysis determine which SSA registers are live
at the beginning of each basic block and which one are killed at
the end of the basic block.
It also includes utilities to simulate the register pressure for loop
fusion and fission.
The implementation is based on the paper "A non-iterative data-flow
algorithm for computing liveness sets in strict ssa programs" from
Boissinot et al.
* Adds new pass for validating non-uniform group instructions
* Currently on checks execution scope for Vulkan 1.1 and SPIR-V 1.3
* Added test framework
The local-single-store-elim algorithm is not fundamentally bad.
However, when there are a large number of variables, some of the
maps that are used can become very large. These large data structures
then take a very long time to be destroyed. I've seen cases around 40%
if the time.
I've rewritten that algorithm to not use as much memory. This give a
significant improvement when running a large number of shader through
DXC.
I've also made a small change to local-single-block-elim to delete the
loads that is has replaced. That way local-single-store-elim will not
have to look at those. local-single-store-elim now does the same thing.
The time for one set goes from 309s down to 126s. For another set, the
time goes from 102s down to 88s.
GCD MIV test as described in Chapter 3 of "Optimizing Compilers for
Modern Architectures: A Dependence-Based Approach" by Randy Allen, and
Ken Kennedy.
Delta test as described in Figure 3 of "Practical Dependence Testing" by
Gina Goff, Ken Kennedy, and Chau-Wen Tseng from PLDI '91.
* Reworked how execution model limitations are checked
* Now OpFunction checks which entry points call it and checks its
registered limitations instead of building a call stack in the entry
point
* New tests
* Moving function to entry point mapping into VState
Relaxs checks for per-vertex builtin variables. If the builtin
decoration is applied to a variable, then those checks now allow a level
of arraying on the variable before checking the type consistency.
* Allows arrays of variables to be present for the per-vertex variables:
* Position
* PointSize
* ClipDistance
* CullDistance
* Updated tests
Add test for case where OpBranch branches to a value (a function value).
Previous tests only checked a label value (name of a block.).
Update validate_id.cpp to remove the TODO for OpBranch and say that it
is already checked in validate_cfg.cpp
The unordered_set in ADCE that holds all of the live instructions takes
a very long time to be destroyed. In some shaders, it takes over 40% of
the time.
If we look at the unique ids of the live instructions, I believe they
are dense enough make a simple bit vector a good choice for to hold that
data. When I check the density of the bit vector for larger shaders, we
are usually using less than 4 bytes per element in the vector, and
almost always less than 16.
So, in this commit, I introduce a simple bit vector class, and
use it in ADCE.
This help improve the compile time for some shaders on windows by the
40% mentioned above.
Contributes to https://github.com/KhronosGroup/SPIRV-Tools/issues/1328.
For each loop in a function, the pass walks the loops from inner to outer most loop
and tries to peel loop for which a certain amount of iteration can be done before or after the loop.
To limit code growth, peeling will not happen if the growth in code size goes above a configurable threshold.
Provides functionality to perform ZIV and SIV dependency analysis tests
between a load and store within the same loop.
Dependency tests rely on scalar analysis to prove and disprove dependencies
with regard to the loop being analysed.
Based on the 1990 paper Practical Dependence Testing by Goff, Kennedy, Tseng
Adds support for marking loops in the loop nest as IRRELEVANT.
Loops are marked IRRELEVANT if the analysed instructions contain
no induction variables for the loops, i.e. the loops induction
variable is not relevent to the dependence of the store and load.
Adding three rules to fold OpDot (implemented as two).
- When an OpDot has two constants, then fold to the resulting const.
- When one of the inputs is the 0 vector, then fold to zero.
- When one of the inputs is a single 1 with 0s, then rewrite to an
OpCompositeExtract of the appropriate element. This will help find
even more folding opportunities.
Contributes to #709.
